Here are the responses I received concerning the best use of Tree Navigation Controls.
In summary, best performance for tree controls comes with tall, shallower trees. Users take longer to find information using a tree menu than with a more traditional index menu, so make sure there are good reasons for choosing the tree control over a more traditional navigational concept.
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From: Klaus Kaasgaard
Not a whole lot of research available on this as far as I know. I looked
around a few months ago for research on menu design and navigation and found the following (summarized):
Most studies conclude that breadth is better than depth. However, while
increased depth harms search performance on the web, a medium condition of
depth and breadth outperforms a shallow web structure.
Comparing an 8x8x8 design, a 16x32 design and a 32x16 design, Larson and
Czerwinski (1998) conclude that: "The reaction time and lostness data
together paint a clear picture that subjects performed best with the 16x32
hierarchy and worst with the 8x8x8 hierarchy.
Larson and Czerwinski's conclusions map into the information foraging
theory. The 16x32 and 32x16 information structures most likely afforded
optimal performance because their category levels were more distinct at top levels (better scent) than those of the 8x8x8 hierarchy.
Source: Larson & Czerwinski: Web Page Design: Implications for Memory,
Structure and Scent for Information Retrieval", CHI 1998.
A recent study compared three menu designs: Index menu layout, cascading
horizontal menu layout, and cascading vertical menu layout.
* Task completion time was significantly lower for the participants using
the index menu layout.
* The horizontal menu design performed poorest both on objective measures
(time on task) and on subjective measures (perceived disorientation,
perceived ease of navigation and perceived frustration).
Source: Bernard & Hamblin: "Cascading versus Indexed Menu design", Usability
News, 2003
Looking forward to hearing your summary on this.
Klaus
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K l a u s K a a s g a a r d
User Experience Research Manager
Yahoo!
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From: Gregor
Jeff,
I'm very interest in hearing what data/feedback you get. I just
implemented a tree structure for a web based hardware appliance and will
be using the same structure for a java based application.
My thought was; expose the prime features and make the drill downs very
discoverable. I think a tall skinny tree can be just as hard to navigate
as a bush.
Thanks,
Gregor
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